It is known that a conventional voltage regulator can be used to regulate a DC voltage supplied to a load such as a microprocessor. For example, a voltage regulator can include a power converter, such as a DC-DC converter, and may include other components such as a controller for controlling operation of the power converter.
An example of a DC-DC converter is a synchronous buck converter, which has minimal components, and therefore is widely used in voltage regulator applications. In an example application, the input voltage to the buck converter is typically 12VDC. An output voltage produced by the voltage regulator may be 5.0VDC, 3.3VDC, or even lower.
Conventional multiphase interleaved voltage regulator power supply topologies can include two or more power converter phases that operate in parallel with each other to convert power and supply power to a corresponding load. Implementation of a multiphase voltage converter topology (as compared to a single voltage converter phase topology) can therefore enhance the output current capability of a power supply system.
A typical configuration of a voltage regulator such as a so-called synchronous buck converter includes an inductor, a high side switch, and a low side switch. During operation, a controller associated with the buck converter repeatedly pulses the high side switch ON to convey power from a power source through the inductor to a dynamic load. The controller repeatedly pulses the low side switch ON to provide a low impedance path from a node of the inductor to ground in order to control an output of the buck converter. Thus, the energy stored in the inductor increases during a time when the high side switch is ON and decreases during a time when the low side switch is ON. During switching operation, the inductor transfers energy from the input to the output of the converter phase.
Today's microprocessors and high performance ASIC chips can operate on low voltages and require a wide range of currents such as less than 1 A (Ampere) and over 100 amperes. A load can operate at these extremes of current for long periods of time. Under such extreme conditions, it is challenging to maintain an output voltage of a power converter within a tolerable range.
Many multi-phase power supplies in use today do not optimize the number of active phases to achieve the best efficiency across a range of load currents. Instead, for simplicity sake, designers often optimize at one point and accept less than optimum efficiency at all other points. The optimization point is frequently some intermediate current.
However, attempts have been made to increase the efficiency of voltage regulators that support such wide swings in output current. For example, it is known that certain buck converters are more efficient at a higher end of a respective operational range than at a lower end of the range. To increase the efficiency of a converter over a wide current range, controllers sometimes implement phase shedding techniques. That is, at lower current values in a range, fewer phases of a respective multi-phase power supply are activated. At higher current values within a range, more phases of a multi-phase power supply are activated to power a respective dynamic load.
More specifically, today's microprocessors and high performance ASIC chips can operate from low voltages and require high currents. In applications such as microprocessor and graphics processor power delivery, the load can range from low (1 A to 20 A) to high (>100 A). Often the processor will operate at an average current that is around 50-70% of maximum.
Due to the increasing cost of electricity and environmental harm caused by creating electricity, there is a need to have high DC-DC conversion efficiency optimized the range of load currents. In multiphase buck switching regulators supporting low-voltage high-current applications, the number of phases is chosen to optimize the efficiency at high load currents where the losses are the largest. This results in less than optimum efficiency at lighter loads where a large number of phases are not needed.